Air conditioning system



Feb. 16, 1937. w, RQESSLER 2,071,178

AIR CONDITIVCNING SYSTEM Filed June 18, 1935 Room Humidishat 3 Inventor:

Edward W Roesslev, y His Attorney.

Room Thermostat Patented Feb. 16, 1937 UNITED STATES AIR CONDITIONING SYSTEM Edward W. Roessler, Schenectady, N. Y., assignor to General ElectricCompany. a corporation of New York Application June 18, 1935, Serial No.-27,158

6 Claims.

My invention relates to systems for conditioning the air within rooms or enclosures.

The load imposed on air conditioning systems varies widely with changes in the temperature of the air admitted to the system for conditioning. For example, in the winter when a room or other enclosure is being heated by such a system, the amount of heat required on relatively warm days will be much less than that required on cold days. If a heating system is made to operate at its highest efilcency on a cold day, there will be a loss in efliciency on warmer days. It has been proposed to overcome this disadvantage by providing a plurality of units for heating or for cooling the air and by operating only the number of units required for a given temperature of the air admitted to the conditioner, each unit being operated under substantially full load conditions; The efilciency of air conditioning systems utilizing refrigerating machines for both heating and cooling may be increased greatly by such an arrangement.

It is an object of my invention to provide an air conditioning system employing a heat exchange surface, the effective area of which is varied dependent upon the temperature of air admitted to the system and the operation of which is controlled in response to the temperature of the air within the enclosure to be conditioned Another object of my invention is to provide an improved air conditioning system utilizing a plurality of heat exchanging elements or units and so arranged that the number of elements which may be operated is automatically varied with the changes in temperature of the air admitted to the system.

Another object of my invention is to provide an air conditioning system having a plurality of heat exchange elements or units and so arranged that the number of units in operation is determined by the temperature of the air admitted to the system while the operation of the units is controlled by the temperature of the air within the enclosure to be conditioned.

. A further object of my invention is to provide an improved air conditioning system of the type utilizing refrigerating machines as heat pumps both for heating and for cooling the air to be conditioned.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of, novelty 0 which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing, the single figure of which shows diagram- 5 matically an air conditioning system and control therefor embodying my invention.

Referring now to the drawing, I have shown an air conditioning system including a duct l0 through which air is circulated and conditioned and then discharged into an enclosure ll. Outdoor or fresh air is admitted to the duct through an intake passage l2 and room air for recirculation enters the duct through a passage l3. The fresh air and room air are mixed and circulated through the duct where the mixture is conditioned and then forced into the room or enclosure ll through an outlet passage 14 by operation of a fan or blower iii. The outdoor or fresh air admitted to the duct is cleaned by a filter IS in the passage l2 and the room or recirculated air is cleaned by a filter I! in the passage l3.

A plurality of heat exchange elements l8, I9, 20, and 2| are pnovided for varying the temperature of the air circulated through the duct I0. For purposes of illustration, the heat exchange elements I8, i9, 20, and2l have been shown as condensers or radiators of refrigerating machines I, 2, 3, and 4 respectively, including compressors 22, 23, 24, and 25 respectively, and evaporators 26, 21, 28, and 29 respectively. Compressors 22, 23, 24, and 25 are connected to be driven by motors 22a, 23a, 24a, and 25a, respectively. The evaporators 26, 21, 28, and 29 are arranged to absorb heat from a heat source such as a body of water 30 contained within a tank or other vessel and supplied from some suitable source such as a deep well of substantially constant temperature and which can supply a suflicient volume of water for the maximum heating requirements of the system. Refrigerating machines are particularly suitable for systems of this type since they may be utilized either to heat or to cool the heat exchanging elements associated with them, it being possible to construct a refrigerating machine with a reversible refrigerant circuit so that either one of the heat exchanging elements thereof may be the evaporator or the condenser, as desired.

In the system shown, the refrigerant circuits of machines 2 and 3 can be reversedto cool the air in the duct Illby pumping heat from the air in the duct to thesource of heat 30, condensers I9 and 20 operating as evaporators and evaporators 21 and 28 operating as condensers. 55

orators.

Machines 2 and 3 are therefore available either to heat or to cool the air to be conditioned. Machines I and 4 are not reversible and are utilized only when it is desired to heat by pumping heat from the source to the air in the duct III.

The refrigerant circuits of machines I and 4 are similar and with the exception of the compressors, condensers and evaporators, the corresponding parts of the refrigerant circuits of these two machines have been designated by the same numerals. During the operation of machines I and 4, the compressors 22 and 25 deliver' compressed gaseous refrigerant through conduits 3| to condensers I8 and 2|. The gaseous refrigerant is liquefied in condensers I8 and 2I by dissipation of heat to the air .in duct I0 and the liquid refrigerant flows through conduits 32 to liquid receivers 33. The liquid refrigerant is then admitted to evaporators 2B and 29 through conduits 34 by operation of thermostatic expansion valves 35. The valves 35 are operated to maintain a predetermined temperature on the suction side of the evaporators, thermostatic bulbs 36 containing a volatile liquid being secured on the suction side of the evaporators to operate the valves 35 through tubes 31. The liquid refrigerant admitted to evaporators 26 and 29 is vaporized by the absorption of heat from the source 30 and is withdrawn from the evaporators and returned to compressors 22 and 25 through conduits 38.

The refrigerant circuits of reversible machines 2 and 3 are also similar and with the exception of the compressors, condensers, and evaporators, corresponding parts of the refrigerant circuits of these machines have been designated by the same numerals. Several manually operated valves employed for reversing the machines have been marked with the letter 1) and are indicated as open or closed, these valves being shown in their positions when machines 2 and 3 are pumping heat from the source 30 to condensers I9 and 20.

During the normal or heating operation of machines 2 and 3, with the manual valves in the positions shown, compressors 23 and 24 deliver gaseous refrigerant through valves 39 and conduits 40 to condensers I9 and 20. The gaseous refrigerant is cooled by dissipating heat to the air circulating through condensers I9 and 20 and is liquefied, the liquid refrigerant flowing through valve 4| into liquid receivers 42. From the receivers 42 the liquid flows through valves 43 and thermostatic expansion valves 44 to evaporators 21 and 28, the expansion valves 44 being operated by thermostatic bulbs 45 secured to the suction sides of the evaporators. Gaseous refrigerant is withdrawn from the evaporators through conduits 46 and valves 41 and is returned to the compressors.

During the reversed or cooling operation of machines 2 and 3 the manually operated valves marked closed are opened and those marked open are closed. Compressors 23 and 24 then operate to deliver gaseous refrigerant through valves 48 and conduits 49 to evaporators 21 and 28 which act as condensers, cooling and liquefying the refrigerant. The liquid refrigerant then passes through conduits 50 and valves 5| to receivers 42 from which it passes through valves 52 and thermostatic expansion valves 53 to condensers I9 and 20, which now operate as evap- The temperature of the heat exchange devices I9 and 20 is now controlled by expansion valves 53 provided with thermostatic bulbs 54 on the suction sides of these evaporators. The liquid refrigerant absorbs heat from and cools the air in duct I0 and is thereby vaporized, the vaporized refrigerant being withdrawn and returned to the compressors 23 and 24 through conduits 40 and valves 55.

For any given air conditioning system the desirable number and arrangement of the heat exchange elements will be determined upon consideration of the particular requirements of the system and the size and type of machines obtainable. In the system described, the condenser I8 is used as a preheater in the fresh air passage, the heat exchange devices I9 and 20 are arranged as a unit, each device affecting one-half of the air passing through the duct I0, and condenser 2| is arranged entirely across the duct.

In accordance with my invention, the number and order of the heat exchange elements which may be operated to change the temperature of the air passing through the duct are automatically selected in response to the temperature of the fresh air admitted to the duct I2, and the operation of one or more of the elements selected is controlled in response to the temperature of the air within the enclosure to be conditioned. The change of the number of heat exchange elements clearly changes the effective surface area available for varying the temperature of the circulated air. The system may be operated either to heat or to cool the air in the air circulating duct as required, and a humidifier is provided to add moisture to the air when required, but only when the system is set to heat the air in the enclosure.

Referring again to the drawing, three thermostats 56, 51, and 58 are arranged in the fresh air passage l2 and are responsive to the temperature of the fresh air admitted to the duct I0. These three thermostats are connected to select which of the condensers I8, I9, 20, and 2| may be operated and in what order, when it is desired to heat the air supplied to the enclosure II. A thermostat 59 responsive to the temperature of the air in the enclosure II is arranged to control the operation of one or more of the refrigerating machines 2, 3, and 4, depending upon the selection made by thermostats 56, 51, and 58. A threepole transfer switch 60 is provided to change the electrical control circuits from heating position to cooling position, it being shown in its position for heating control. During the cooling operation of the system, machines 2 and 3 operate as a unit and in the arrangement illustrated, no selection is made with changes in outdoor temperatures; thermostats 56, 51, and58 are therefore not effective during cooling and the reversed machines 2 and 3 are controlled directly by room thermostat 59.

For purposes of illustration, specific temperature settings of the thermostats are hereinafter assumed. During the heating of the air in duct I0 when the temperature of the outside air is above 45 F., machine 4 is available for heating and to be operated in response to the room thermostat 59. When the temperature of the outside air is below 45 F., but above 25 F., ma-

chine I runs continuously to heat the fresh airin the duct I2, and machines 2 and 3 are available for heating the heat exchange devices I9 and 20 and for operation in response to the room thermostat 59. When the temperature of the outside air is below 25 F., machines I and 4 run continuously to produce heating of the air, and

machines 2 and 3 are available for heating and operate in response to the thermostat 59.

The operation of, the control circuits during heating will now be described assuming the temperature of the outside air to vary gradually from above 45 F., to below 25 F.

In order to energize the control and power circuits, a three-pole switch 6| is closed. This energizes a motor 62 for driving fan I5, and also energizes one side 63 of the power and control bus, the other side 64 of the bus being connected directly to the source of power. It is evident that none of the control or power circuits can be energized unless the fan I5 is operating to circulate air through duct I8. In order that the control circuits shall be available to control the operation of machines I, 2, 3, and 4, during heating switch 68 must be in the upper closed position shown on the drawing. When the temperature of the outside air entering the passage I2 isabove 45 F., a bi-metallic strip 65 of the thermostat 56 engages a contact 66 thereof. This closes a circuit from a contact 61 on a relay 68 of the room .thermostat 59 to contact 13 of thermostat 51 through lead 69, thermostat 56, lead 66a, pole 18 of switch 68 and a lead H. Bi-metallic strip 12 of thermostat 51 engages contact 13 thereof and continues the foregoing circuit through lead 14, solenoid 15 of a motor operating relay 16 and leads 11 and 18 to the bus 64. If, now, thermostat 59 calls for heat, bi-metallic strip 19 thereof engages contact 88 and closes the circuit of an operating coil 8| of relay 68, the coil circuit including secondary 82 of transformer 83, coil 8|, lead 84, strip 19, contact 88, lead 85, and connection 86. Coil 8| is thereby energized and raises an armature 81 to shift upper and lower arms 88 and 89 respectively of relay 68. The upper arm 88 closes a holding circuit for coil 8| from the secondary 82 through connection 86, a connection 85a, and arm 88. The lower arm 89 closes the circuit through solenoid 15 described above by connecting contact 61 with bus 63 through a connection 89a. Energization of solenoid 15 moves an armature 98 of relay 16 to the left and closes the circuit of motor 25a, connecting the motor to bus 64, through leads 11 and 18 and to bus 63 through leads 9| and 9m. Machine 4 is thereby set in operation to heat air passing through duct I8. When sufiicient heat has been added to the air within the room I I, strip 19 of thermostat 59 will engage a contact 92 thereof which provides a short circuit or shunt around coil 8| through leads 84 and 94 deenergizing coil 8|. Armature 81 then drops out, breaking connection between contact 61 and arm 89 tobus 63 and deenergizing relay solenoids 15, thereby opening the circuit of motor 250. and stopping operation of machine 4. Thermostat 59 will continue to control machine 4 'as long as the temperature of the air entering the passage I2 is above 45 F.

When the temperature of the air entering the passage I2 falls below 45 F., but above 25 F., bi-metallic strip 65 of relay 56 will engage a contact 95 thereof, bi-metallic strip 12 of thermostat 51 will assume a position between contact 13 and a second contact 96 thereof, but engaging neither contact, and a bi-metallic strip 91 of relay 58 will '68, a lead I8I, then in parallel through solenoids I82 of relays I 88 for operating motors 23a and 24a of machines 2 and 3 respectively, thence to lead 18 through a connection I84 and lead 11. When thermostat 59 calls for heat in the manner described above, contact 61 is connected to bus 63 through blade 89 and energizes the circuit just described, thereby energizing solenoids I82, actuating armature I85 of relays I83, thereby connecting motors 23a and24a to leads 11 and 9| and starting the motors." When sufiicient heat has been added to the enclosure II, and strip 19 of thermostat 59 moves to engage contact 92, the connection between contact 61 and bus 63 is broken and motors 23a and 24a are deenergized. Machines 2 and 3 are thus available for heating and are under the control of room thermostat 59. A second control circuit is established from lead 18 through lead 11 and a solenoid I86 of a relay I81 of motor 22a to a lead I88, thence to contact 98, strip 91, a lead I89, and to lead 9| through a pole II8 of switch 68. Since leads 11 and 9| are energized by direct connection with buses 64 and 63 respectively, solenoid I86 is energized, operating an armature III of relay I81 and closing the circuit of motor 22a, thereby operating machine I continuously as long as strip 91 of thermostat 58 is maintained in engagement with contact 98.

If the temperature of the air entering the passage I2 now decreases until it is below' 25. F., bi-metallic strip 12 of thermostat 51 will engage contact 96 thereof. This will establish a circuit energizing the solenoid 15 in parallel with solenoid I86. This circuit may be traced from lead 11 through solenoid 15, lead 14 and strip 12 all in parallel with solenoid I86 and lead I88, the parallel circuits being joined at a point H2, and thence back to lead 9| through contact 98, strip 91 and pole II8, thereby completing the circuit.

Solenoid 15 is then energized to close relay 16 and to start motor 25a; and, since solenoid I86 remains energized, machines I and 4 run continuously. The control circuits of machines 2 and 3 are not changed by further decrease of temperature below 25 F., and these machines are still available for operation in response to room thermostat 59.

If now the temperature of the outside air increases, the operations just described will occur in the reverse order. When the temperature rises above 25 F., continuous operation of machine 4 will be suspended, machine I will be run continuously, and machines 2 and 3 will be under control of the room thermostat. When the temperature rises above 45 F., the operation of machines I, 2, and 3 will be suspended and machine 4 will be placed in operation under control of the room thermostat.

A humidifier H3 is provided to add moisture to the air passing through the duct I8 during the heating operation. This humidifier comprises a. tank II4 arranged at the discharge end of duct I8 and a heater 5 for vaporizing water I I6 contained in the tank. A float II1 arranged to operate electrically a valve H8 in a water supply conduit H9 is provided to maintain a substantially constant level of water in the tank II4. Air drawn by the fan I5 through the duct I8 is caused to pass over the surface of the water II6, a baffle I28 being provided, if desired, to direct the air downwardly against the surface of the water. The control for the humidifier II3 comprises a room humidistat |2I operating a relay I22 which in turn energizes the heater I I5.

'Relay I22 is energized by a transformer comprising a primary winding I23 and a secondary winding I24. The primary winding is connected in a circuit which may be traced from the bus 64 through lead 18, primary I23. lead I25, pole H of switch 80, lead 9|, back to bus 63, through lead Sla. When switch 80 is moved to its lower position, pole I I 0 is opened, and thereby opens the circuit of the primary I23. The room humidistat can therefore operate to control the humidifier only when the system is set for heating, and the switch 60 is in its upper closed position shown in the drawing. The humidifier is inoperative at all other times. Float H1 is arranged to connect contacts I26 and I21 whenever the water I I 6 falls below a predetermined level. This completes a circuit from bus 64, lead 18, contacts I21 and I26, a connection I28, a valve operating solenoid I29 and back to bus 63 through lead 9Ia. The solenoid I29 is arranged to operate valve I I8 to supply water to the tank II4 through an inlet pipe I30. Humidistat I 2| is provided with a contact making member I3I which-engages a contact I32 to operate the humidifier II3 when the relative humidity in the enclosure is below the desired value, and a contact I33 to stop operation of the humidifier II3. When the Dole III) of switch 60 is closed, as shown, if member I3I of the humidistat engages contact I32, a circuit is established from the secondary I24 through lead I34, lead I35, member I3I, a lead I44 and a solenoid I36, and back to the secondary I24. Energization of solenoid I36 raises armature I31 and closes arms I38 and I 39. Arm I38 when closed establishes a holding circuit for solenoid I36 through transformer I24, connection I34 and connection I40, to arm I38 and solenoid I36. Arm I39 closes a circuit from lead 9Ia and a lead I4I to heater H5 and through a connection I42 to lead 18, thereby energizing the heater H5, heating the water H6 and supplying moisture to the air passing through duct I0. When the contact member I 3I engages contact I33, the solenoid I36 is short-circuited through leads I43 and I44 and the armature I31 drops out, opening blade I 39 and deenergizing the heater II5, thereby decreasing or stopping the supply of moisture to the air.

When it is desired to operate the air conditioning system to cool the air passing through duct I0, the manually operated valves of machines 2 and 3 are moved to their positions opposite those in which they are shown in the drawing to reverse the operation of machines 2 and 3 in the manner previouslydescribed. In order to prevent operation of machines I and 4 to heat the all passing through the duct I0 when machines 2 and 3 are reversed, switch 60 is moved to its lower position, opening poles 10 and H0 and moving the pole I00 from upper contact I00a td a lower contact I00b. This opens the control circuits of machines I and 4, and establishes a circuit from bus 63 through connection 89a, arm 89, contact I45 of room thermostat relay 68 through a. lead I46, pole I00, lead IOI, solenoids I02 in parallel, connection I04, and leads 11 and 18 to bus 64. In this manner solenoids I02 are energized, which operate armatures I05, thereby closing relays I03 and energizing motors 23a and 24a to drive machines 2 and 3. Machines 2 and 3 operate to pump heat out of the air flowing through duct I8, thereby cooling the air. Should the temperature of the air within the enclosure II be lowered below a predetermined desired value, strip 19 of thermostat 59 will engage the contact 80 and energize coil 8I of relay 68 to lift the armature 81 and disengage arm 83 from contact I 45. This deenergizes solenoids I02 and opens the motor circuits. When the temperature oi the air within the enclosure II has risen to a predetermined value, thermostat 68 will then call for cooling, strip 13 engaging contact 82 and shorting coil BI, thereby causing armature 81 to drop out and reestablish a circuit through solenoid I02, thereby starting machines 2 and 3 to again cool air circulating through duct I0.

From the foregoing it is evident that I have provided a system for conditioning the air within an enclosure and which may be employed at any season of the year, either to heat or to cool the enclosure. Furthermore I have provided an air conditioning system which may be operated at high efliciency regardless of changes in the temperature of the air admitted to the system. It is further evident that I have provided a. simple and effective arrangement for determining the number and order of operation of a plurality of heat exchange units of an air conditioning system.

While I have disclosed a particular embodiment of my invention in connection with an air conditioning system utilizing refrigerating machines as heat pumps, various modifications will occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the embodiment shown and described and I intend in the appended claims to cover all modifications thereof which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A system for conditioning the air within an enclosure including a duct for admitting air to said enclosure, means for circulating air through said duct, means including a plurality of heat exchange elements arranged in said duct for varying the temperature of the air passing therethrough, means including a plurality of sources for supplying a heat exchanging medium to said elements, each of said elements being supplied by a separate one of said sources, means responsive to the temperature of the air entering said duct for selecting the number of said heat exchange elements and of said sources which may be operated, and means independent of said last-mentioned means and responsive to the temperature of the air within said enclosure for controlling the operation of at least one of said sources of supply selected by said last mentioned means.

2. A system for conditioning the air within an enclosure including a duct for admitting air to said enclosure, means for circulating air through said duct, a source of heat, means including a plurality of refrigerating machines arranged to pump heat from said source for heating the air circulating'through said duct, each of said refrigerating machines having a condenser arranged in said duct and an evaporator arranged to receive heat from said source, means responsive to the temperature of the air admitted to said duct for selecting the number of said machines which may be operated, and means responsive to the temperature of the air within said enclosure for controlling the operation of at least one of the machines selected by said last mentioned means.

3. A system for conditioning the air within an enclosure including a duct for admitting air to said enclosure, means for circulating air through said duct, a source of heat, a plurality of refrigerating machines, each of said machines having a condenser and an evaporator, said condensers being arranged in said duct to heat the air circulating therethrough said evaporators being arranged to receive heat from said source, means for reversing at least one of said machines to cool the air circulating through said duct and for preventing operation of the others of said machines, and means responsive to the temperature in said enclosure for regulating said machines when heating and when cooling the air circulating through said duct.

4. A system for conditioning the air within an enclosure including a duct for admitting air to said enclosure, a plurality of heat dissipating elements arranged within said duct, a source of heat, a plurality of heat absorbing elements arranged to'receive heat from said source, a plurality of heat pumping means for pumping heat from said heat absorbing elements to said heat dissipating elements, each of said heat pumping means being connected to pump heat from a separate one of said heat absorbing elements to a separate one of said heat dissipating elements, means responsive to the temperature of the air admitted to said duct for selecting the number of said plurality of heat pumping means which may be operated, and means responsive to the temperature of the air within said enclosure for controlling the operation of at least one of said heat pumping means selected by said last mentioned temperature responsive means.

5. A system for conditioning the air within an enclosure including a duct for admitting air to saidenclosure, a plurality of heat dissipating elements arranged within said duct, a source of heat, a plurality of heat absorbing elements arranged to' receive heat from said source, a plurality of heat pumping means for pumping heat from said heat absorbing elements to said heat dissipating elements, each of said heat pumping means being connected to pump heat from a separate one of said heat absorbing elements to a separate one of said heat dissipating elements, means responsive to the temperature of the air admitted to-said duct for selecting the number of said plurality of heat pumping means which may be operated, means responsive to the temperature of the air within said enclosure for controlling the operation of at least one of said heat pumping means selected by said last mentioned temperature responsive means, means for reversing the operation of at least one of said heat pumping means to pump heat from the air within said duct to said source of heat and to cool the air within said duct and for preventing the operation of the remainder of said plurality of heat pumping means, and means responsive to the temperature of the air within said enclosure for controlling the operation of said heat pumping means.

6. A system for conditioning the air within an enclosure including a duct for admitting air to said enclosure, a plurality of heat dissipating elements arranged within said duct, a source of heat, a plurality of'heat absorbing elements arranged to receive heat from said source, a plurality of heat pumping means for pumping heat from said heat absorbing elements to said heat dissipating elements, each of said heat pumping means being connected to pump heat from a separate one of said heat absorbing elements to a separate one of said heat dissipating elements, means responsive to the temperature of the air admitted to said duct for selecting the number of said plurality of heat pumping means which may be operated, means responsive to the temperature of the air within said enclosure for controlling the operation of at least one of said heat pumping -means selected by said last mentioned temperature responsive means, means for reversing the operation of at least one of said heat pumping means to pump heat from the air within said EDWARD W. ROESSLER. 

